Why do some guys get intimidated when I make the first move?

I'm a very straight foward no bullshit type of person. The weird thing is that I just started to hang out with this guy and after a couple dates I noticed he was very shy. I then proceeded to make the first move. I kissed him and we kissed for a while but he ended up stopping and saying he had to get going. He later told me he felt uncomfortable that I made the first move. This had happened before! Why is is such a bad thing?